1. Field of the Invention
This invention relates to an optimum shift timing indicating device for a vehicle, and more particularly to an optimum shift timing indicating device suitable for use in a motor vehicle provided with a manual transmission and an electronically controlled fuel injection engine.
2. Description of the Prior Art
Recently, with the possible dry-up of petroleum resources in the near future being forcasted, the reduction of fuel consumption of the vehicles such as motor vehicles has become one of the social demands. In general, the fuel consumption of the motor vehicle varies to a considerable extent depending on not only the fuel consumption performance of an engine but also the driving manner of a driver, and hence, a desire has been voiced for a device which instructs the driver about the optimum driving methods suitable for the present running condition of the engine, since an ordinary driver does not have a satisfactory knowledge about motor vehicles. With this end in view, heretofore, there has been put to use a so-called economy meter for indicating an engine load by the intake vacuum, a so-called drive computer for calculating and indicating a fuel consumption per unit running distance (Km/l) or the like. However, the above-described methods present such disadvantages that the effect on fuel consumption is not necessarily satisfactory because they cannot give the driver information about "what measure should be taken then?" in either case.
Therefore, a device may be proposed in which the optimum gear position (chosen in accordance with an engine speed or a running speed of a vehicle and an engine load, taking into consideration the fuel consumption performance and the running performance as shown in FIG. 1) is stored in a memory, a gear position at present (which is calculated from the engine speed and the vehicle speed) is compared with the optimum gear position for example, and, if the gear positions are different from each other, the optimum gear position is displayed. However, the device of the type described has been disadvantageous in that many data maps are needed which indicate the optimum gear positions corresponding to all of the gear positions (five speeds in the example shown in FIG. 1) of the transmission. The process becomes complicated because the present gear position is calculated and compared with the optimum gear position and a large memory capacity is required.